1. Field of the Invention
The present invention generally relates to a power converter, and in particular, to a switching power converter.
2. Description of Related Art
A switching power converter is applicable in a buck power regulator, and generally includes a DC/DC controller, an upper-bridge switch, a lower-bridge switch, and an impedance circuit composed of elements such as inductors and regulated capacitors. The switching power converter controls the conduction of the upper-bridge switch and the lower-bridge switch by the DC/DC controller, thereby adjusting the current flowing through the impedance circuit. Accordingly, the switching power converter can convert an input voltage into a corresponding output voltage.
In actual operation, in response to changes in conversion efficiency accompanying the load change, most of the existing switching power converters switch to different conduction modes according to the load, so as to improve the output efficiency. For example, in U.S. Pat. No. 6,433,525 issued to Intersil Company, whether a polarity of an inductor current is changed is used to determine the switch between a pulse-width modulation (PWM) mode and a pulse-frequency modulation (PFM) mode, and a counter is used to delay the switching timing of the two conduction modes.
In the above technology, the counter is needed to count the time at which the status of a load begins to change, that is, the counter is used to provide hysteretic switching mechanism. However, as a determination time of the counter must be spent on determining whether to switch the mode in the prior art, the overall response rate of the system is affected. In addition, the hysteretic switching provided by the counter increases the complexity of the hardware structure of the system.